Phase transition method of amorphous material using cap layer

ABSTRACT

The present invention provides a phase transition method of an amorphous material, comprising steps of: depositing the amorphous material on a dielectric substrate; forming a cap layer on the amorphous material; depositing a metal on the cap layer; and crystallizing the amorphous material. According to the present invention, the surface of the amorphous material is protected by the cap layer, so that clean surface can be obtained and the roughness of the surface can be remarkably reduced during thermal process and sample handling. In addition, the cap layer is disposed between the amorphous material and the metal to diffuse the metal, so that the metal contamination due to the direct contact of the metal and the amorphous material in the conventional method can be remarkably reduced.

This application is a National Stage application under 35 U.S.C. § 371of and claims the benefit of International Application No.PCT/KR03/02362, filed on Nov. 6, 2003, published in the English languageon May 21, 2004 as International Publication Number WO 2004/042805 A1,which claims priority to Korean Application No. 10-2002-0068994 filed onNov. 8, 2002, all of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a phase transition method of anamorphous material, and more specifically, to a method phase transitionmethod of an amorphous material capable of implementing a uniform thinfilm without any contact of a metal and the amorphous material.

BACKGROUND ART

A thin film transistor (TFT) is a switching device in which apolysilicon thin film is used as an active layer. In general, the thinfilm transistor is used as an active device of an active matrix liquidcrystal display apparatus, a switching device of an electro-luminescencedisplay apparatus, and peripheral devices thereof.

The thin film transistor is typically manufactured by using a directdeposition process, a high temperature process, or a laser thermaltreatment process. By using the laser thermal treatment process, acrystallization (or a phase transition) can be obtained even at a lowertemperature of 400° C. or less, and high field effect mobility can beimplemented. Therefore, the laser thermal treatment process has beenmore popular than the direct deposition process and the high temperatureprocess. However, the laser thermal treatment process has problems thatthe phase transition is not uniform and the associated apparatuses ofhigh price are required. In addition, since the productivity of thelaser thermal treatment process is low, it is not suitable formanufacturing the polysilicon on a wide-area substrate.

The other method of crystallizing the amorphous material, particularly,the amorphous silicon is a solid-phase crystallization method capable ofobtaining a uniform phase transition by using the associated apparatusesof low price. However, the method also has problems that the time of thecrystallization is too long and the productivity is too low. Inaddition, since the temperature of the crystallization is high, a glasssubstrate can not be used.

On the other hand, a phase transition method of the amorphous materialby using a metal has an advantage that the phase transition can beobtained at a low temperature in a short time in comparison with thesolid-phase crystallization method. Therefore, many researches have beenmade on the method. The method includes a metal induced crystallizationmethod.

In the metal-induced crystallization method, a specific kind of metal isdirectly contacted with at least one portion on the thin film of theamorphous material. And then, the phase transition is performedlaterally from the contacted portion. Otherwise, the metal is doped intothe thin film of the amorphous material to achieve the phase transitionof the amorphous material. The examples are illustrated in FIGS. 1 a to1 c.

Now, the conventional metal-induced crystallization method will bedescribed in detail. Firstly, a buffer layer 20 is formed on adielectric substrate 10. And then, an amorphous material 30 is depositedon the buffer layer 20 by a chemical vapor deposition (CVD) method.Next, an oxide film is formed as a cap layer 40 (see FIG. 1 a).

After the cap layer 40 is formed, the cap layer 40 is patterned by usinga photolithography, so that a metal can be in contact with at least oneportion of the amorphous material 30. The metal 50 is deposited on thepatterned cap layer 40 and the amorphous material 30 which is exposed bythe patterning process. Next, a thermal treatment is performed topartially grow grains 32 and 34 in the amorphous material, so thatphase-transitioned thin films 32 and 34 can be obtained (see FIG. 1 b).

However, in the conventional method of performing the phase transitionon the amorphous material, the characteristics of the correspondingdevice are deteriorated due to the metal contamination on the regionwhere the amorphous material 30 is directly contacted with the metal 50.Therefore, an additional process of removing the region is necessary, sothat the productivity of the devices may be drastically lowered.

In addition, in the case where source and drain regions in a transistorare patterned to form a thin film or in the other case where one of thesource and drain regions in the transistor are patterned to form thethin film, there is a problem that the amorphous material can not becompletely phase-transitioned and the amorphous material region 37remains (see FIG. 1 c).

Namely, although the conventional metal-induced crystallization methodof the amorphous material has an advantage of reducing the temperatureof the crystallization, there is the problem that the intrinsiccharacteristics of the thin film are deteriorated by the contaminationdue to the metal which is permeated into the phase-transitioned thinfilm.

As a result, in order to use the metal-induced crystallization method ofthe amorphous material, it is necessary to minimize the metalcontamination of the thin film. In order to minimize the contaminationof the thin film, the most important thing is to reduce the amount ofthe metal used therein. The approaches disclosed to solve these problemsinclude one method where metal ions having a concentration of 10¹² to10¹⁴ cm⁻² are deposited by using an ion implantation apparatus and thena high temperature process, a rapid thermal treatment process, or alaser illumination process is performed. And, it also includes the othermethod where a viscous organic thin film and a liquid-phase metal aremixed in the convention metal-induced crystallization method, adeposition process is performed by a spin coating method, a thermaltreatment process is performed, and then, the amorphous material isphase-transitioned.

However, the disclosed approaches have failed to effectively prevent thesurface contamination of the thin film during crystallization. Inaddition, the approaches still have problems in terms of increasing thesize of the grains and improving their uniformity

DISCLOSURE OF INVENTION

The present invention is contrived to solve the aforementioned problem,and an object of the present invention is to provide a phase transitionmethod by which the phase transition of an amorphous material can beobtained without any direct contact of the metal and the amorphousmaterial and a metal contamination of the thin film and the othercontaminations due to a thermal treatment process can be reduced.

Another object of the present invention is to provide a phase transitionmethod by which the thin film having grains in a uniform size can beimplemented by using even an infinitesimal amount of the metal, wherebyany metal etching process is not necessary and thus the productivity canbe improved.

Still another object of the present invention is to provide acrystallization method by which the amount of the metal diffused intothe amorphous material can be controlled by using the thickness of thecap layer and the deposition conditions of the cap layer.

In order to achieve the objects, an aspect of the present invention is aphase transition method of an amorphous material, comprising steps of:depositing the amorphous material on a dielectric substrate; forming acap layer on the amorphous material; depositing a metal on the caplayer; and performing a phase transition on the amorphous material.

In the aspect of the present invention, it is preferable that the methodfurther comprises a step of depositing a buffer layer before the step ofdepositing the amorphous material on the dielectric substrate.

In addition, in the aspect of the present invention, it is preferablethat the method further comprises a step of performing a preliminarythermal treatment before the step of performing a phase transition onthe amorphous material.

In addition, in the aspect of the present invention, it is preferablethat the method further comprises a step of removing the metal and thecap layer after the step of performing a phase transition on theamorphous material.

Another aspect of the present invention is a phase transition method ofan amorphous material, comprising steps of: depositing a metal on adielectric substrate; forming a buffer layer on the metal; depositingthe amorphous material on the buffer layer; and performing a phasetransition on the amorphous material.

In addition, in the aspect of the present invention, it is preferablethat the method further comprises a step of performing a preliminarythermal treatment and a step of patterning the thermally-treated filmafter the step of depositing the amorphous material and before the stepof performing a phase transition on the amorphous material.

In addition, in the aspect of the present invention, it is preferablethat the method further comprises a step of depositing a second caplayer on the metal, and a step of patterning the stack structure afterthe step of depositing the metal before the step of performing a phasetransition on the amorphous material.

In addition, in the aspect of the present invention, it is preferablethat the dielectric material is a material selected from glass, quartz,a single crystal wafer covered with an oxide film, or a thin metalsubstrate covered with an insulator.

In addition, in the aspect of the present invention, it is preferablethat the amorphous material is an amorphous silicon.

In addition, in the aspect of the present invention, it is preferablethat the cap layer is a single film comprising one selected from asilicon nitride film, a silicon oxide film, and an organic film, or adouble film comprising a silicon nitride film and a silicon oxide film.

In addition, in the aspect of the present invention, it is preferablethat the cap layer comprises a first part and a second part which aredifferent from each other.

In addition, in the aspect of the present invention, it is preferablethat the first part is formed to be a single film and the second part isformed to be a double film.

In addition, in the aspect of the present invention, it is preferablethat the cap layer is deposited by a PECVD method.

In addition, in the aspect of the present invention, it is preferablethat the thickness of the second cap layer is in a range of 0.1 to 1000nm.

In addition, in the aspect of the present invention, it is preferablethat the deposition of the metal is performed by using an ionimplantation, a PECVD, a sputter, a shadow mask, or a coating of aliquid-phase metal dissolved in an acid solution, a spin coating of amixture of an organic film and a liquid-phase metal, or a gas containinga metal.

In addition, in the aspect of the present invention, it is preferablethat the metal is partially patterned by using one selected form aphotolithography, a photoresist, and a shadow mask.

In addition, in the aspect of the present invention, it is preferablethat the metal is deposited to have a surface density in a range of 10¹²to 10¹⁸ cm⁻².

In addition, in the aspect of the present invention, it is preferablethat the metal is deposited to have a thickness of 1000 nm or less.

In addition, in the aspect of the present invention, it is preferablethat the metal is nickel.

In addition, in the aspect of the present invention, it is preferablethat the buffer layer is a layer selected from a silicon nitride filmand a silicon oxide film.

In addition, in the aspect of the present invention, it is preferablethat the preliminary thermal treatment is performed at a temperature of200 to 800° C.

In addition, in the aspect of the present invention, it is preferablethat the secondary phase transition of the amorphous material isperformed by at least one method selected from a thermal treatmentmethod, a rapid thermal treatment method, and a laser illuminationmethod.

In addition, in the aspect of the present invention, it is preferablethat the thermal treatment is performed at a temperature of 400 to 1300°C.

In addition, in the aspect of the present invention, it is preferablethat the thermal treatment is performed by one selected from a halogenlamp, a ultraviolet lamp, and a furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentinvention will become apparent from the following description ofpreferred embodiments given in conjunction with the accompanyingdrawings, in which:

FIGS. 1 a to 1 c are cross-sectional views illustrating a phasetransition method of a conventional amorphous material;

FIGS. 2 a to 2 d are cross-sectional views illustrating an embodiment ofa phase transition method of an amorphous material according to thepresent invention;

FIG. 3 is a cross-sectional view illustrating another embodiment of aphase transition method of an amorphous material according to thepresent invention;

FIG. 4 is a cross-sectional view illustrating still another embodimentof a phase transition method of an amorphous material according to thepresent invention;

FIGS. 5 a to 5 c are cross-sectional views illustrating further stillanother embodiment of a phase transition method of an amorphous materialaccording to the present invention;

FIGS. 6 a to 6 d are cross-sectional views illustrating anotherembodiment of a phase transition method of an amorphous materialaccording to the present invention;

FIGS. 7 a to 7 c are cross-sectional views illustrating still anotherembodiment of a phase transition method of an amorphous materialaccording to the present invention;

FIGS. 8 a and 8 b are optical microscope photographs of apolycrystalline silicon which is crystallized by a phase transitionmethod according to the present invention;

FIGS. 9 a to 9 c are optical microscope photographs of a polycrystallinesilicon which is crystallized by a phase transition method according tothe present invention and illustrate dependency on an amount of a metal;

FIGS. 10 a and 10 b are atomic force microscope photographs ofpolycrystalline silicon thin films which are crystallized by the presentinvention and a conventional technique, respectively;

FIG. 11 is a graph illustrating a degree of an oxidation on a surface ofa silicon thin film.

FIGS. 12 a to 12 c are optical microscope photographs illustratingresults of phase transitions depending on ratios [NH₃]/[SiH₄]; and

FIG. 13 is a graph of reflectance of a thin film for illustratingdegrees of crystallization of the specimens of FIG. 12.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the preferred embodiments according to the present invention willbe described in details with reference to the accompanying drawings. Thesame parts are referred to as the same name although they are indicatedwith different reference numerals.

FIGS. 2 a to 2 d are schematic views illustrating a preferred embodimentof the present invention. The material that is thermally treated in thepresent invention comprises a dielectric substrate 100, a buffer layer200 deposited on the dielectric substrate 100, an amorphous material 300deposited on the buffer layer 200, a cap layer 400 formed on theamorphous material 300, and a metal 500 deposited on the cap layer 400(see 2 a).

The dielectric substrate 100 is not limited to a specific material.However, it is preferable that the dielectric material a materialselected from glass, quartz, a single crystal wafer covered with anoxide film is used as the dielectric material in order to ensure theuniformity of the temperature during the phase transition of theamorphous material and the uniformity of the thin film.

The buffer layer 200 is not an essential component in the process.However, if it is deposited, the buffer layer is preferably a layerselected from a silicon nitride film and a silicon oxide film.

The amorphous material 300 is not limit to a specific material, but itmay include an amorphous silicon.

The cap layer 400 has functions of diffusing the metal uniformly intothe amorphous material layer and protecting the thin film from anunnecessary metal contamination. The cap layer 400 is preferably made upof one of a silicon nitride film, a silicon oxide film, an organic film,and it is also formed with a double film comprising a silicon nitridefilm and a silicon oxide film.

The deposition of the cap layer 400 is preferably performed at atemperature of 650° C. or less. The deposition method is not limited toa specific method, but a PECVD (plasma enhanced chemical vapordeposition) method is preferable.

In addition, the cap layer is preferably formed to have its thickness ina range of 0.1 to 1000 nm.

The deposition of the metal 500 is performed by using one method of anion implantation method, a PECVD method, a sputter method, and a shadowmask method. Otherwise, the deposition is performed by using a coatingof a liquid-phase metal dissolved in an acid solution, a spin coating ofa mixture of an organic film and a liquid-phase metal, or a gascontaining a metal. Therefore, the deposition method is not limited to aspecific method.

In addition, the metal 500 is preferably deposited to have its surfacedensity in a range of 10¹² to 10¹⁸ cm⁻² and its thickness of 1000 nm orless. The metal used herein is not limited to a specific metal, butnickel is preferable.

The phase transition method of the amorphous material 300 is performedby one of a thermal treatment method and a method using a laser. Thethermal treatment may be performed by using a halogen lamp, anultraviolet lamp, a furnace, or the like, but it is not limited to them.

In addition, the phase transition of the amorphous material 300 isperformed by a method using one of an electric field and a magneticfield.

In addition, it is preferable that the thermal treatment is performed ata temperature of 400 to 1300° C. The thermal treatment is performed byone selected from a rapid thermal treatment method in the aforementionedtemperature range and a long-term thermal treatment method. Moreover,both of the methods may be used for the thermal treatment.

The rapid thermal treatment method is a method of repeating multipletimes of thermal treatments for tens of seconds at a temperature of 500to 900° C. The long-term thermal treatment method is a method ofperforming a thermal treatment for longer than one hour at a temperatureof 400 to 500° C.

If the phase transition of the amorphous material 300 is achieved, themetal 500 is diffused into the cap layer 400. Therefore, within theamorphous material 300, nuclei of metal disilcide (MSi₂, precipitates)are formed to be laterally grown. As a result, grain boundaries 340 areformed between the grains 320 (see FIG. 2 c).

On the other hand, the grains 320 continue to be laterally grown, sothat the boundaries 340 are gradually narrowed. As a result, theamorphous material is completely phase-transitioned into apolycrystalline material (see FIG. 2 c).

After the amorphous material is completely phase-transitioned, the metal500 and the cap layer 400 are removed by an etching process. Finally,the polycrystalline film can be obtained in accordance with the presentinvention.

On the other hand, in order to more completely crystallizing theamorphous material, a preliminary thermal treatment may be performed ata temperature of 200 to 800° C. before the step of the phase transitionof the amorphous material, or a secondary phase transition which is thesame as the phase transition may be performed on the amorphous material.

The preliminary thermal treatment is performed by one of theaforementioned thermal treatment methods.

FIG. 3 which is another embodiment of the present invention illustratesa phase transition method where the cap layer 400 is formed with twoparts and then the phase transition of the amorphous material isperformed. In the embodiment, it is sufficient for the cap layer 400 tocomprise first and second parts having different thicknesses. The caplayer is not limited to a structure of the first part having a singlefilm and the second part having a double film.

In particular, in the embodiment, it is preferable that a lower portionof the second part is made up of the same material as that of the firstpart. Moreover, the upper and lower portions of the second part may bemade up of different materials.

FIG. 4 which is still another embodiment of the present inventionillustrates a phase transition method where the metal 500 on the caplayer 400 is partially patterned and then the phase transition of theamorphous material is performed. In the embodiment, the partialpattering of the metal 500 is performed by using one of aphotolithography, a photoresist, and a shadow mask.

FIGS. 5 a to 5 c which are still another embodiment of the presentinvention illustrate steps in a phase transition method of an amorphousmaterial 300 where a metal 500, a buffer layer 200, and the amorphousmaterial 300 are sequentially deposited on a dielectric substrate 100.In the embodiment unlike the other embodiments, the metal 500 isdiffused through the buffer layer 200 upwardly, and thus, the respectivegrains 320 within the amorphous material 300 deposited on the bufferlayer 200 are grown toward the grain boundaries 340, so that theamorphous material is gradually changed into a polycrystalline material(see FIGS. 5 a to 5 c).

FIGS. 6 a to 6 d are further still another embodiment of the presentinvention. In the embodiment, a buffer layer 200, an amorphous material300, a cap layer 400, and a metal 500 are sequentially deposited on adielectric substrate 100 (see FIG. 6 a). Next, a preliminary thermaltreatment is performed on the amorphous material 300 (see FIG. 6 b). Andthen, the thermally-treated metal 500, the cap layer 400, and theamorphous material 300 are patterned (see FIG. 6 c). Next, the phasetransition is performed on the amorphous material 300, and then, themetal 500 and the cap layer 400 are removed (see FIG. 6 d). By thesesteps, the amorphous material is phase-transitioned.

FIGS. 7 a to 7 c are further still another embodiment of the presentinvention. In the embodiment unlike the embodiment shown in FIGS. 6 a to6 d, the step of depositing a second cap layer 400′ on the depositedmetal layer 500 is further comprised. As a result, the metal layer 500constructed to have two cap layers above and below the metal layer.

After the completion of the deposition, before the phase transitionbeing performed on the amorphous material, the amorphous material 300,the first cap layer 400, the metal layer 500, and the second cap layer400′ are patterned by a photolithography using a photoresist (see FIG. 7b). Next, the amorphous material 300 is crystallized, and then, thefirst cap layer 400, the metal 500, and the second cap layer 400′ areremoved (see FIG. 7 c). By these steps, the amorphous material isphase-transitioned.

For the various embodiments shown in FIGS. 3 to 7, the components, thedeposition methods of the components, and the phase transition method ofthe amorphous material shown in FIG. 2 are adapted, as they are. Inaddition, the secondary phase transition of the amorphous material isalso adapted.

FIGS. 8 to 10 illustrate photographs of the polycrystalline siliconeswhich are obtained by using silicon as an amorphous material in thepreferred embodiments according to the present invention.

FIGS. 8 a and 8 b illustrate cases of phase transitions. In these cases,glass is used as the dielectric substrate and the amorphous siliconhaving a thickness of 50 nm is deposited on the buffer layer. Inaddition, the silicon nitride film having a thickness of 150 nm isdeposited as the cap layer, and nickel of 10¹³ cm⁻² is deposited as themetal layer. Next, a thermal treatment is performed at a temperature of430° C. for one hour. And then, multiple times of thermal treatment areperformed at a temperature of 750° C. in a time interval of 20 seconds.

FIG. 8 a shows a result of a phase transition by repeating 5 times ofthermal treatments at a temperature of 750° C. for 20 seconds. FIG. 8 bshows a result of a phase transition by repeating 20 times of thermaltreatments under the same condition. In the figures, it can beunderstood that the grains are laterally grown. In particular, it can beunderstood that, as the thermal treatments are more repeated, thequality of polycrystalline is getting better and better.

FIGS. 9 a to 9 c illustrate cases of phase transitions. In these cases,glass is used as the dielectric substrate, a silicon oxide film having athickness of 100 nm is deposited as the buffer layer, and the amorphoussilicon having a thickness of 50 nm is deposited. In addition, thesilicon nitride film having a thickness of 60 nm is deposited as the caplayer, and nickel is deposited as the metal layer. In these cases, apreliminary thermal treatment is performed at a temperature of 500° C.for 5 minutes, as the amount of the metal is varied. And then, 20 timesof thermal treatment are performed at a temperature of 750° C. for 20seconds.

FIGS. 9 a, 9 b, and 9 c correspond to the cases of nickel being 5×10¹²cm⁻², 8×10¹² cm⁻², and 10¹³ cm⁻², respectively. As shown in thesefigures, it can be understood that as the amount of the metal isincreased, the size of the grain is getting smaller and smaller.

FIGS. 10 a and 10 b illustrate surfaces of silicon thin films as theamorphous materials which are phase-transitioned by the metal beinginduced according to the conventional method (FIG. 10 a) and the presentinvention (10 b), respectively. In the present invention, the cap layerhaving a thickness of 60 nm is formed, and then, the amorphous materialis crystallized, so that the RMS roughness of the polycrystallinesilicon thin film is 0.92 nm. On the other hand, the RMS (root meansquare) roughness in the conventional method is 1.33 nm. As a result, itcan be understood that the film of the present invention has the betterroughness than that of the conventional method.

FIG. 11 is a graph illustrating a degree of an oxidation on a surface ofa silicon thin film depending on the presence of the cap layer.

One case is that the cap layer of a nitride film is provided to have athickness of 350 nm. The other case is that the cap layer is notprovided. As shown in FIG. 11, it can be understood that the surface ofthe silicon thin film of the case where the cap layer is provided hasless oxygen than that of the case where the cap layer is not provided,although the other process conditions are the same.

FIGS. 12 and 13 are views illustrating aspects of silicon thin filmcrystallization depending on the concentration of nitrogen in thenitride film used as the cap layer.

In FIG. 12, FIGS. 12 a, 12 b, and 12 c are optical microscopephotographs illustrating results of the phase transitions where the caplayer are formed to have the same thicknesses of 50 nm and ratios[NH₃]/[SiH₄] of 35, 65, and 100, respectively. Herein, in the phasetransitions, the other process conditions are the same. As shown in FIG.12, it can be understood that, in the cases of FIGS. 12 b and 12 c, thecomplete crystallization is obtained and the grains have a shape ofcircle or hexagon. In addition, it can be understood that the grainhaving a shape of hexagon is formed by the adjacent grains beingabutted.

On the other hand, it can be understood that, in the case of FIG. 12 a,complete crystallization is not obtained and the incomplete crystals aredispersed to have a shape of circle.

Herein, the sizes of the grains of FIG. 12 b and 12 a are 14 μm, and 10μm, respectively. Therefore, the most amount of the metal, nickel can beobtained in the case that the ratio [NH₃]/[SiH₄] is 100. As a result, itcan be understood that, as the ratio [NH₃]/[SiH₄] is larger, thediffusion rate of the metal is increased.

Accordingly, it can be understood that the amount of the metal can becontrolled by using the ratio [NH₃]/[SiH₄].

FIG. 13 is a graph of reflectance of a thin film by using illuminationof a ray of 273 nm ultraviolet light for illustrating degrees ofcrystallization of the specimens of FIG. 12. As shown in FIG. 13, in thecase of the ratio [NH₃]/[SiH₄] being 35, the reflectance has no peak inthe ultraviolet region, and in the cases of the ratios being 65 and 100,the reflectance has its peak. Therefore, it can be understood that, themetal-induced crystallization can be controlled depending on thecondition of the deposition of the nitride film.

Although the present invention and its advantages have been described indetails, it should be understood that the present invention is not limitto the aforementioned embodiment and the accompanying drawings and itshould be understood that various changes, substitutions and alterationscan be made herein by the skilled in the arts without departing from thespirit and the scope of the present invention as defined by the appendedclaims.

INDUSTRIAL AVAILABILITY

According to the present invention, it is advantageous that the caplayer is disposed between the amorphous material and the metal todiffuse the metal, so that the metal contamination due to the directcontact of the metal and the amorphous material, which is a problem inthe conventional method, can be remarkably reduced.

In addition, according to the present invention, it is advantageous thatthe cap layer is formed on the amorphous material, so that thecontamination or the oxidation on the surface of the thin film of theamorphous material can be prevented.

Furthermore, according to the present invention, although the cap layeris additionally provided, the cap layer can be formed withoutdestructing the vacuum ambient in the process chamber while theconventional process of deposition of the amorphous material and themetal is performed. Therefore, it is advantageous that the process canbe easily performed.

In addition, according to the present invention, it is advantageous thatthe amount of the metal can be controlled and the degree of thecrystallization can be controlled by adjusting the concentration ofnitrogen in the nitride film which is formed as the cap layer.

Moreover, according to the present invention, it is advantageous thatthe amount of precipitates of the metal disilicide formed in the thinfilm of the amorphous material can be controlled by adjusting theconcentration of nitrogen in the nitride film which is formed as the caplayer, and thus, the phase-transitioned thin film having a high qualitycan be implemented.

1. A phase transition method of an amorphous material, comprising stepsof: depositing the amorphous material on a dielectric substrate; forminga cap layer on the amorphous material; depositing a metal having asurface density in a range of 10¹² to 10¹⁵ cm⁻² on the whole surface ofthe cap layer; depositing a second cap layer on the metal; patterningthe stack structure after the step of depositing the metal; andperforming a phase transition on the amorphous material after the stepof patterning.
 2. The phase transition method of an amorphous materialaccording to claim 1, wherein the method further comprises a step ofdepositing a buffer layer before the step of depositing the amorphousmaterial on the dielectric substrate.
 3. The phase transition method ofan amorphous material according to one of claim 2, wherein the bufferlayer is a layer selected from a silicon nitride film and a siliconoxide film, or a double layer comprising a silicon nitride and a siliconoxide films.
 4. The phase transition method of an amorphous materialaccording to claim 1, wherein the method further comprises a step ofperforming preliminary thermal treatment before the step of performing aphase transition on the amorphous material.
 5. The phase transitionmethod of an amorphous material according to claim 4, wherein the methodfurther comprises a step of patterning the thermally-treated film afterthe step of performing preliminary thermal treatment before the step ofperforming a phase transition on the amorphous material.
 6. The phasetransition method of an amorphous material according to claim 4, whereinthe preliminary thermal treatment is performed at a temperature of 200to 800° C.
 7. The phase transition method of an amorphous materialaccording to claim 1, wherein the method further comprises a step ofremoving the metal and the cap layer after the step of performing aphase transition on the amorphous material.
 8. The phase transitionmethod of an amorphous material according to one of claim 1, wherein themethod further comprises a step of performing a secondary phasetransition on the phase-transitioned material after the step ofperforming the phase transition on the amorphous material.
 9. The phasetransition method of an amorphous material according to claim 8, whereinthe secondary phase transition of the amorphous material is performed byat least one method selected from a thermal treatment method, a rapidthermal treatment method, and a laser illumination method.
 10. The phasetransition method of an amorphous material according to claim 9, whereinthe thermal treatment is performed at a temperature of 400 to 1300° C.11. The phase transition method of an amorphous material according toclaim 9, wherein the thermal treatment is performed by one selected froma halogen lamp, an ultraviolet lamp, and a furnace.
 12. The phasetransition method of an amorphous material according to claim 9, whereinan electric field or a magnet field is applied in the thermal treatmentprocess.
 13. The phase transition method of an amorphous materialaccording to claim 1, wherein the dielectric substrate is a materialselected from glass, quartz, a single crystal wafer covered with anoxide film, and a thin metal substrate covered with a dielectric film.14. The phase transition method of an amorphous material according toone of claim 1, wherein the amorphous material is an amorphous silicon.15. The phase transition method of an amorphous material according toclaim 1, wherein the cap layer is a single film comprising one selectedfrom a silicon nitride film, a silicon oxide film, an organic film, or adouble film comprising a silicon nitride film and a silicon oxide film.16. The phase transition method of an amorphous material according toclaim 1, wherein the cap layer comprises a first part having a thinthickness and a second part having a thick thickness.
 17. The phasetransition method of an amorphous material according to claim 16,wherein a lower portion of the second part is made up of the samematerial as that of the first part.
 18. The phase transition method ofan amorphous material according to claim 16, wherein an upper portion ofthe second part is made up of the same material as or the differentmaterial from that of the first part.
 19. The phase transition method ofan amorphous material according to claim 1, wherein the cap layer isdeposited by a PECVD method.
 20. The phase transition method of anamorphous material according to claim 19, wherein the deposition isperformed at a temperature of 650° C. or less.
 21. The phase transitionmethod of an amorphous material according to claim 1, wherein thethickness of the cap layer is in a range of 0.1 to 1000 nm.
 22. Thephase transition method of an amorphous material according to claim 1,wherein the thickness of the second cap layer is in a range of 0.1 to1000 nm.
 23. The phase transition method of an amorphous materialaccording to one of claim 1, wherein the deposition of the metal isperformed by using an ion implantation, a PECVD, a sputter, a shadowmask, or a coating of a liquid-phase metal dissolved in an acidsolution, a spin coating of a mixture of an organic film and aliquid-phase metal, or a gas containing a metal.
 24. The phasetransition method of an amorphous material according to claim 1, whereinthe metal is partially patterned by using one selected form aphotolithography, a photoresist, and a shadow mask.
 25. The phasetransition method of an amorphous material according to one of claim 1,wherein the metal is deposited to have a thickness of 1000 nm or less.26. The phase transition method of an amorphous material according toone of claim 1, wherein the metal is nickel.
 27. The phase transitionmethod of an amorphous material according to one of claim 1, wherein thephase transition of the amorphous material is performed by at least onemethod selected from a thermal treatment method, a rapid thermaltreatment method, and a laser illumination method.
 28. The phasetransition method of an amorphous material according to claim 27,wherein the thermal treatment is performed at a temperature of 400 to1300° C.
 29. The phase transition method of an amorphous materialaccording to claim 27, wherein the thermal treatment is performed by oneselected from a halogen lamp, an ultraviolet lamp, and a furnace. 30.The phase transition method of an amorphous material according to claim27, wherein an electric field or a magnet field is applied in thethermal treatment process.